Lab #3

Part 4: THE STEREOSCOPIC DISSECTING MICROSCOPE
Up until now you have been exclusively using a compound light microscope. While it is ideal for
viewing tiny microbes that can be mounted on a slide, there are biological specimens that are
too large and/or thick to be mounted on a slide and viewed with the compound microscope (yet
too small for the naked eye). In this case you will want to use the stereoscopic dissecting
microscope or “dissecting microscope” for short. Two advantages of this microscope are 1) you
can manipulate your specimen (turn, flip, dissect) using your hands or tools while viewing it
under magnification (hence term “dissecting”), and 2) by looking through both oculars you can
see the image in three dimensions (“stereoscopic”).
The dissecting microscope is a simple light microscope since the image you see is magnified
through a single magnification lens. Your microscope has two such lenses that you can switch
between, allowing you to view your specimen at 15X or 30X. While the total magnifications
possible on this microscope are low, they provide the advantages of a very large field of view
and a very thick depth of focus. This will allow you to see most, if not all, of your specimen
clearly and in three dimensions.
Your dissecting microscope contains a single focus knob and two different light sources
controlled by knobs on either side of the arm of your microscope. Turn them on and you will
notice that one light source is below the stage and the other is above the stage. The light below
the stage produces light that will pass through a transparent specimen, what we call
transmitted light. The light above the stage produces light that will bounce or reflect off the
specimen. We refer to this as reflected light, which is used to illuminate a non-transparent
specimen from above.